1. Field of the Invention
The present invention relates to synthetic oligo- and polypeptides, compositions containing same, and methods of use, including the treatment of viral infections.
2. Brief Description of the Background Art
Generally speaking, antiviral therapy has proceeded along two separate but interrelated pathways. The first is the development of compounds that act by directly influencing the virus/host cell interaction as a means of aborting the infection. The second is more broadly directed at altering the host's immune functions to prevent viral entry or enhance viral clearance at the level of the host organism. Both approaches have required identification of the specific viral agent in question and detailed understanding of the events of viral replication, in terms of molecular interactions at the cellular level and pathogenic mechanisms at the level of the entire host (see generally Server, A. C. and Wolinsky, J. S., Human Motor Neuron Diseases, edited by Lewis P. Rowland (Raven Press, New York, 1982), the chapter entitled "Approaches to Antiviral Therapy," at pp. 519-546.)
Among specific antiviral chemotherapeutic agents are drugs that interfere with virus adsorption to, penetration into, and uncoating in the host cell. Inhibition of these early steps in virus replication, which occur prior to utilization of a significant number of host processes, would be associated with limited host toxicity. Few drugs, however, have been shown to act at these steps in virus infection. Among these are included heparin, amantadine, and a number of oligopeptides.
It has been suggested that a number of carbobenzoxyoligopeptides, which inhibit infection by some members of the herpes, orthomyxovirus, and paramyxovirus families may act by preventing virion penetration. Activity of these agents in culture was independently reported by several groups in 1968. See, for example, Miller, F. A. et al., Appl. Microbiol. 16: 1489-1496 (1968); or Nicolaides, E. et al., J. Med. Chem. 11: 74-79 (1968). Carbobenzoxy D-phenylalanine-L-phenylalanyl-nitro-L-arginine (SV-4814) is among the most effective of these agents, with the greatest activity shown against measles virus (Miller, F. A. et al., supra). The site of action of this agent in inhibiting measles virus infection has been demonstrated (Norrby, E., Virology 44: 559-608 (1971)). SV-4814 has no effect on virus adsorption or virus-induced hemagglutination, yet it markedly prolongs the period during which adsorbed virions are susceptible to neutralization by extracellular antibody. It has been concluded therefore that the drug inhibits virion penetration, which, in the case of measles, is thought to occur by fusion of virion envelope with the host cell membrane. The activity of the drug is generally thought to derive from its sequence homology with the amino-terminus of the viral protein that mediates fusion (fusion, or F, protein). For example, Richardson, et al. (Virology 105: 205-222 (1980)), has demonstrated that the inhibition of paramyxovirus activity by SV-4814 and closely related oligopeptides was amino acid sequence-specific. For example, in the case of Sendai virus, the most effective inhibitor was the oligopeptide with the closest sequence homology to the aminoterminus of the viral fusion protein.
Although the ultimate value of these peptides as clinically useful antiviral agents still remains to be determined, preliminary studies indicate that these inhibitors of the prior art have limited toxicity in vitro and can be safely administered orally to laboratory animals. Richardson, et al., supra, have also demonstrated that oligopeptides with activity against measles and other paramyxoviruses and at least one orthomyxovirus (influenza A) can be synthesized, pointing to a great potential for these agents.
Among oligopeptides of relevance to those claimed in the present invention can be mentioned the following: Cbz--D--Phe--L--Phe--Gly (where Cbz is the carbobenzoxy group), Cbz--L--Phe--L--Phe, Cbz--D--Phe--L--Phe--L--(NO.sub.2)Arg, Cbz--Gly--L--Phe--L--Phe, and Cbz--Gly--L--Phe--L--Phe--Gly (see Server and Wolinsky, supra, p. 523). These oligopeptides are inhibitors of Sendai virus activity. Cbz--Phe--D--Ala has also been tested against measles and herpes viruses (see Nicolaides, E. et al., supra).
It would be of great interest to extend the antiviral peptide findings of the prior art to other viral species, including mumps virus.
The fusion (F) protein of mumps virus is composed of two disulfide-linked glycopeptides, F.sub.1 and F.sub.2, that are generated by proteolytic cleavage of a precursor (F.sub.o) glycopeptide chain (see, for example, Rima, et al., J. Gen. Virol. 46: 501-505 (1980), or Merz, et al., Ibid 64: 1457-1467 (1983)). Studies of the F.sub.1 N-terminus of mumps virus have been hampered by the difficulty in obtaining sufficient quantities of purified protein.
It appeared worthwhile, however, to initiate and carry out an investigation of mumps virus in order to provide further potentially clinically useful antiviral peptides.